The printers of the prior art are generally installed with automatic cutting paper device, which generally consists of the mutually cooperated top-cut blade part and down cut-blade blade part, thereof, the top cut-cut blade part further comprises the top-cut blade which can move up and down, and the drive unit comprising motor, worm and cam mechanism. While the down-cut blade part comprises the fixed installed down-cut blade, paper cutting unit and installing support, where both the down-cut blade and the paper cutting unit are installed on the installing support. The installing support itself can be pivotally installed on the mainframe of the printer. Under normal operation condition, when paper is required to be cut after being printed, program operated in the controller of the printer will send instruction to the drive unit of the top-cut blade part, enabling the top-cut blade to move downward to the setting position where paper can be cut off, then return to the home position automatically. If for some reason, for example: paper is stuck between the top-cut blade and the down-cut blade, enabling the top-cut blade fails to return automatically, then the top-cut blade will be partially blocked at the outside of the down-cut blade, enabling the maintenance personnel fails to directly open the down-cut blade part. On the other hand, for protection need, under the circumstance that the top-cut blade fails to return to the home position due to being jammed, after the passing of the set homing time or in the case of detecting abnormal motor operation, the controller will cut off power source of the motor, so as to avoid motor burnout. At this time, blade withdrawal mechanism is needed, and manual intervention is required, so as to shoot the trouble. For the blade withdrawal mechanism of the prior art, it is just the setting of a window simply at the top-cut blade part to enable the worm to expose partially, thus maintenance personnel can poke the worm manually, drive the top-cut blade to return to the home position artificially, and clear paper and conduct other maintenance work by opening the down-cut blade part after the return of the top-cut blade. However, such structure wastes time and energy at handling troubles such as paper jam, and the efficiency is low. Therefore, it is indeed necessary to improve the prior art.